Well, its been a while since I messed with individual pedals but I would say that the biggest difference you can make this way is by putting one before your distortion/overdrive pedal (if you use one) which would control the level of distortion just like winding back your guitars volume control ( but likely without rounding the tone ) and one after the distortion pedal which will just control your overall volume level.If you are using a delay it is possible that you could have a volume pedal to control the level of the delayed signal only which would be cool but you would have to use a splitter box or cable to route things.